Separation of particles based on size is one of the essential components in biochemical analysis, environmental assays, and industrial and biomedical applications. Filtration is one of the most frequently used techniques to separate particles. A mechanical filter can be used to remove, filter, or collect particles. This filtering and collection of particles can be used for sampling of particles, chemical detection, and/or biological cell analysis.
Existing filtration methods are performed in a batch or a continuous manner. However, when the particle size is much smaller or when the difference in particle size is smaller, separation becomes difficult. Pore clogging or membrane fouling may be an issue.
Separation of specific cells from a mixed cell population is important in medicine for biological and immunological measurements, and for use in cell therapy (e.g. transfusion medicine). For example, in the medical field, it is often necessary to filter blood. Human blood cell separation is the first challenging step towards total blood count and the subsequent disease diagnosis, prognosis and management. Normal erythrocytes vary in dimension from 5 μm to 8 μm. Leukocytes have an average diameter of between 7 μm to 20 μm.
Several techniques are available for separation of blood elements. Most current approaches involve centrifugation (e.g. distinguishing the cells based on density) or surface characteristics. Such procedures are typically not able to separate all of the white blood cells from the platelets and the forces involved in separation of the cells can damage the final product. Cell labeling-based separation techniques are expensive, inconvenient and in most cases, labeled cells cannot be infused in patients and the harsh washing conditions necessary to remove the label can damage the cells. Passive matrix-based separation techniques are not sufficiently selective or adaptive for separation of specific cell types. Similarly, column chromatography and magnetic bead adsorption techniques cannot separate cell subtypes quickly and cheaply.
Therefore, there is a need to develop devices and methods for continuous separation of particles of different sizes, in particular, the separation of various cells and particles that exist in blood. The present invention satisfies these and other needs.